lst = [1,4,9,16,2,5,10,15]
l=len(lst)
lst_new=[]
for i in range(l):
    for j in range(i+1,l):
        lst_new.append(lst[i]+lst[j])
        break # 你这里break了，每个内层循环只执行一次，为什么还要用循环呢
print(lst_new)

修改版
lst = [1,4,9,16,2,5,10,15]
l=len(lst)
lst_new=[]
for i in range(l):
    lst_new.append(lst[i]+lst[i+1])
print(lst_new)


# 不错
